Broken shaft....and what else? - Page 2 - SailNet Community
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post #11 of 14 Old 07-02-2010
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If the shaft is broken, don't you worry about the whole shaft sliding out, thus leaving a very large hole in the bottom of the hull?


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post #12 of 14 Old 07-06-2010
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Mine broke 2 months ago. I sailed 45 miles home and my marina got me in my slip. The repair cost was $3K including haul out and in. My shaft is only 3/4" and mine is a direct drive. I posted here and concluded the primary cause was alignment - fatigue failure. The new shaft is Aquamet 22 (supposedly the best steel for shafts). I have no idea what the old shaft was made of. Also, I have a dripless shaft seal that was made before they came out with the vent tube. The break was inside the seal so I do believe the heat in the area of the seal contributed to the break. Your situation is lots more complicated than mine so I don't believe this info. really helps you.
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post #13 of 14 Old 07-07-2010 Thread Starter
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Thanks Harbin2, it sounds like my shaft may have met the same fate as yours. I am still uncertain whether there is some kind of coupling or universal joint in the shaft between the stuffing box and the transmission that could have become disconnected or broken, but if not then it appears the fracture occurred to the part of the shaft to the aft of the suffing box flange and just forward of the through hull.
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post #14 of 14 Old 07-07-2010
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A couple thoughts that are very remote, but haven't been mentioned so here goes in an effort to save you some hauling charges if the situation, by chance, is less severe than a broken shaft.

When you did the 'you turn your end while I hold mine still' test - were you certain to be grasping actual shaft on both ends? or is it possible one person was grasping a zinc, strut, prop or other anscilliary appendage? If you're uncertain, repeat the test - you can do this on a short haul and may even be able to do it while in the water.

If it truely is broken, not only are you going to have to replace it, you're going to want to determine the cause. I've seen a bronze shaft crack like a twig when it struck a log - but only after years of use without proper zinc protection. The pitting was so severe the entire matrix of the shaft was comprimized. SO the lesson is, be sure your zincs are working.

I will repeat for emphasis the importance of alignment - even in a v-drive. a simple check on this is to eyeball the attitude of the engine side prop shaft end relative to the transmission coupling while taking the shaft throu a "+" manuever in the shaft log. this will require removal of any stuffing box or similar device, and it's not an alignment process as much as it is a test on whether the alignment is WAY of of whack. IF it is, it will be very clear to you the at one or more of the 4 endpoints of the "+" motion (up to stop, down to stop, starboard, port) you will notice that the travel does not leave the shaft equidistant from the coupling - if this is true, it's likely to be your root cause of the break. That said, it would be very surprising that a loud noticiable noise or vibration underfoot would not have been experienced prior to the damage.

good luck.
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